Polyurethane and polyisocyanurate foam insulation boards are commonly employed in the construction industry. These insulation boards are cellular in nature and typically include an insulating compound trapped within the cells of the foam. For example, it is common to produce insulation boards by employing hydrochlorofluorocarbons as a blowing agent, which thereby entraps these compounds within the cell network for purposes of improving the insulating ability of the foam.
Because fluorinated and chlorinated carbon compounds, such as hydrochlorofluorocarbons, may have a deleterious impact on the environment, many governments have or will prohibit the use of these compounds in the manufacture of foam. Many alternative blowing agents have been proposed including the use of certain hydrocarbons. In particular, pentane and isomers of pentane have been employed as blowing agents with a relative degree of commercial success. For example, blends including cyclopentane together with isopentane are commonly employed as a substitute for halogenated carbon compounds.
The presence of the cyclopentane has advantageously provided useful short-term insulation values (i.e., R values). Cyclopentane, however, is expensive. Also, cyclopentane is believed to partially solubilize polyurethane and polyisocyanurate polymers, and therefore its presence within the cells of the insulation board may deleteriously impact dimensional stability or deleteriously impact long-term R values. Furthermore, this ability to solubilize the foam material ultimately leads to poorer or higher diffusion rates which has a deleterious effect on long-term R values.
There is therefore a need to improve upon the hydrocarbon-based blowing agent systems currently employed in the manufacture of foams, particularly polyisocyanurate foams.